The present invention relates to an apparatus for providing a continuous shift of speed reduction ratio of the output shaft relative to the input shaft as a function of the output shaft load torque. During the operation of a motor vehicle, there are many different load conditions to which a motor vehicle is subjected. Prominent of these load generating conditions include, but are not limited to, inertia, rolling resistance, and gravity during hill climbing. Spark-Ignition, Turbine, and Compression-Ignition engine equipped vehicles, particularly, are limited in their ability to provide sufficient torque while maintaining acceptable overall engine efficiency over such a wide range of load conditions due to the inherent narrow useable power band of said engines. It is, therefore, necessary to equip said vehicle with a transmission that is capable of amplifying the engine torque as is necessary to accomodate external loads that are encountered by the vehicle, and to decrease the speed reduction ratio of the output shaft relative to the input shaft during light load conditions to promote a relatively higher efficiency of the engine.
One solution to the aforementioned problem is to install a transmission in the power train from which several predetermined fixed reduction ratios can be selected either manually by the operator, or by a transducer so mounted that the reduction gearing arrangement is engaged hydraulically upon the appropriate signal from the transducer. A fixed reduction ratio transmission has the inherent drawback that it often forces the engine to operate in an inefficient portion of the engine useable powerband, causing fuel waste, excessive engine wear, and poor vehicle performance.